Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/58—Moulds
  • B29C44/588—Moulds with means for venting, e.g. releasing foaming gas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/3402—Details of processes or apparatus for reducing environmental damage or for working-up compositions comprising inert blowing agents or biodegradable components
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/56—After-treatment of articles, e.g. for altering the shape
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/56—After-treatment of articles, e.g. for altering the shape
  • B29C44/5609—Purging of residual gas, e.g. noxious or explosive blowing agents
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2110/00—Foam properties
  • C08G2110/0083—Foam properties prepared using water as the sole blowing agent
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S521/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S521/918—Physical aftertreatment of a cellular product

Definitions

• the invention relates to production of porous materials. It is of general application but is -% . . . . described in particular in relation to the production of plastic foams, and especially polyurethane foams.
• polymeric foams by reactive chemical routes are varied and well known.
• An example of such polymeric materials is flexible polyurethane foam which is produced in blocks typically 2 meters x 2 meters x 1 meter. These large blocks can be produced either continuously on conveyor type machines or discontinuously in molds.
• Flexible polyurethane foam is formed by a reaction between a high molecular weight polyol and a diisocyanate. This reaction is highly exothermic reaching a peak, as depicted in a time/temperature curve, typically within about 5 to 30 minutes. Polyurethane foam therefore have to be transferred to an intermediate "cure area" promptly after initial cure where they are carefully stacked with air space around each block until they have cooled. A large area is required for this purpose and the blocks typically need to be stored for a minimum of 10 hours before they can be restacked or loaded for transporting to the customer. This process of intermediate storage, to ensure adequate cooling of the blocks, is inconvenient and costly in space - requirements. Further, the intermediate storage area contains a large number of blocks of inflammable foam
• a newer approach is to deliberately draw cool air through an initially cooled polyurethane block.
• the composition of the air, at least as to moisture content, may be controlled, but such control alone has been found insufficient to achieve satisfactory results. Cool air drawn through the block removes heat, volatile gases, sublimates and excess water from the block.
• Polyurethane foam commonly contains butylated hydroxy-toluene (“BHT” full name 2,6-ditertiarybutyl- 4-methyl phenol) , which is used as an antioxidant in the polyols that are reacted with isocyanates such as toluene diisocyanate (“TDI' 1 ) to form the foam.
• BHT is a solid subliming at 70°C and therefore taken up in cooling air passed through blocks exhibiting an. initial temperatures of 140°C or higher.
• the cooling air is desirably recycled for heat recovery, control of moisture content, and to prevent uncontrolled levels of residual isocyanate or auxiliary blowing agents such as chlorofluorocarbons ("CFCs") or other volatile compounds such as methylene chloride or 1,1,1-trichloroethane from reaching the atmosphere.
• CFCs chlorofluorocarbons
• Canadian patent application 2,017,991 and 2,017,992 disclose another approach utilized for rapid cooling of porous materials. These process provide a partial solution for the problem with volatiles taken up from the hot material and later separating out and blocking heat exchangers. These applications discloses a process wherein the blocking problem is prevented by mixing heated gases co ing from a first part of a cooling zone, and carrying the volatiles, with cold gases extraneous or coming via a heat exchanger from a second or subsequent part of the cooling zone, so that the volatiles separate out.
• the mixed gases which are passed through the porous material in the second or subsequent part of the cooling zone are substantially filtered within the porous material rather than in the heat exchanger.
• a process and plant for cooling of porous materials are disclosed. Specifically, the process concerns blocks of polyurethane or other open cell foamed plastics prepared from an exothermic reaction of foam forming materials.
• volatiles within the porous blocks are taken up by cooling gases and separate out therein on cooling of the gases below a separation (i.e.
• sublimation or condensation temperature characterized by: i) effecting the cooling of the porous materials in two or more successive zones, ii) mixing gases emerging from the first zone, carrying the volatiles, with gases at a lower temperature, particularly gases emerging from the second or subsequent zones and thereafter cooled by heat exchange, whereby the temperature of the mixed gases is brought below the separation temperature, and iii) passing the mixed gases through the porous material to filter out the separated volatiles.
• first gases are passed through the porous material in a first zone to cool the porous material and to remove volatiles therefrom in a first gas mixture which exits the porous material.
• the flow rate of the first gases through the porous material is controlled to provide a controlled, uniform cooling rate thereof.
• This first gas mixture is combined with second gases having a lower temperature to form a second gas mixture having a temperature which is sufficiently low to condense one or more of the volatiles.
• the second gas mixture is passed through the porous material in a second zone to filter condensed or sublimed volatiles thereon and to further cool the porous material. It is also desirable to remove particulate matter from the first gas mixture prior to mixing with the second gases. Also, particulate matter may optionally be removed from the second gases prior to mixing with the first gases. This removes certain materials from the gas streams and prevents later buildup on the heat exchangers which are utilized to cool the gas.
• Conventional foaming materials contain a substantial amount of solvent or auxiliary blowing agents such as chlorofluorocarbons which are released into cooling gas currents during the exothermic curing cycle. High concentrations of such compounds in the cooling gas necessitates recycling if emission of pollutants is to be avoided..
• Water is a preferred foaming agent for forming polyurethane foam. Water reacts with an isocyanate group to form an intermediate carbamic acid which liberates carbon dioxide gas. However, as desirable as water is during the foaming phase of polyurethane form production, it may later deleteriously effect the foam by terminating free isocyanate groups as discussed above. Thus, water is normally used in combination with other blowing agents.
• a uniform distribution of free isocyanate groups is required for producing foam with a predictable degree of cross-linking (and therefore stiffness and hardness) . It would be desirable to utilize an increased amount of water in the polyurethane formulation so as to provide sufficient foaming without utilizing toxic auxiliary foaming agents. It would be of further advantage to simultaneously eliminate excess water during later curing of the foam which would otherwise interfere with polyurethane cross-linking.
• What is needed is a method of rapidly cooling polyurethane foam wherein the heat liberated during exothermic reaction is controlled so as to prevent slow oxidation or outright ignition of the foam.
• a method for fabricating polyurethane foam is needed wherein the polyurethane foam formulation includes a greater quantity of water as a foaming agent without causing interference with cross- linking of the polyurethane, thereby reducing or eliminating the need for utilizing toxic auxiliary foaming agents.
• a method for rapidly cooling polyurethane foam following initial polyurethane foam formation wherein oxidation or ignition associated with exothermic curing of the polyurethane is prevented.
• the method of the present invention also allows the use of novel polyurethane foam forming formulations which include a greater quantity of water as a foaming agent so as to minimize or obviate the need for auxiliary blowing agents while achieving satisfactory foaming and foam properties.
• the method of the present invention removes excess water remaining after the foaming of the polyurethane so as to prevent the water from interfering with cross-linking of the foam.
• This method provides rapid cooling of polyurethane foam blocks and enables physical qualities equal to blocks which are conventionally cured, while at the same time, decreasing the emission of pollutants.
• Figure 1 illustrates a side elevated view of one embodiment of an apparatus of the present invention
• Figure 2 is an internal view of the apparatus of Figure 1;
• Figure 2A is a partial top view of a slat conveyor for use in the apparatus of Figure 1;
• Figure 3A and 3B are flow charts illustrating emissions generated during the method of the present invention when two different polyurethane formulations are utilized;
• Figure 4 is a side view of porous blocks located upon a conveyor passing through an enclosed tunnel utilized in one embodiment of the present invention (internal view of tunnel) ;
• Figure 5 is a top view of the conveyor of Figure
• Figure 6 is a cross-sectional view of the second section of an enclosed tunnel illustrating the recycling of cooling gas
• Figure 7 is a schematic drawing illustrating the temperature gradients and air paths within the enclosed tunnel
• Figure 8 is a side view of a vertical foam block apparatus positioned adjacent and supplying blocks to the apparatus of Figure 1;
• Figures 9 to 19 are graphical illustrations of temperature vs time for cooling of various polyurethane foam blocks.
• polyurethane foam blocks are subjected to ambient air cooling just after a peak is reached in the time/temperature curve of the exothermic polyurethane reaction.
• the internal block temperature of the polyurethane ranges from about 250 to 500°F and usually about 370 to 400°F.
• excess moisture refers to that quantity of water not utilized in the foaming of the polyurethane which, if allowed to remain as a vapor in the block, would interfere with further curing.
• it is preferred to dehumidify the air prior to drawing it through the block so as to increase the capacity of the air to remove excess water from the material, while at the same time preventing the ambient air from introducing additional water therein.
• the temperature of the ambient air after passing through the foam block will generally range from about 160 to 180°F.
• ambient air is recirculated through the foam block.
• the ambient air recirculated through the foam block removes additional heat, moisture, and sublimates therein. After the ambient air is recirculated through the foam block, it is mixed with fresh additional chilled ambient air.
• fresh refers to ambient air not having passed through the block.
• water removes isocyanate groups from TDI which would otherwise be utilized for further cross- linking reactions with hydroxyl groups of polyols.
• an increased amount of water sufficient to yield substantially all of the foaming required in a polyurethane foam material may be utilized in a polyurethane formulation.
• the present invention advantageously obviates or minimizes the use of auxiliary foaming agents heretofore necessary to provide sufficient foaming. Since auxiliary foaming agents result in emissions that are ecologically harmful, the present invention allows the use of an environmentally harmonious alternative polyurethane foam formulations.
• the temperature of the air exiting the first section via the first section of the enclosed tunnel of the present invention ranges from about 150 to 185 ° F.
• the first section vents directly to the atmosphere, the reduction or elimination of toxic auxiliary blowing (or foaming) agents such as chlorofluorocarbons from the polyurethane formulation minimizes the environmental effect of such venting.
• the second cooling step forces both fresh (non-recycled) cooled air and recycled air through the polyurethane foam block.
• Fresh ambient air is constantly added to the recycled air which, as explained above, contains sublimates such as TDI and BHT.
• sublimates such as TDI and BHT.
• the cooling means utilized in the apparatus of the present invention provides a reduction of ambient air temperature such that the mixture of ambient and recycled air in the second step exhibits a temperature range of from about 100 to 160°F.
• BHT condenses at temperatures below about 70 ° C (158 ° F) , any extracted BHT vapors will precipitate in the second section. Since the cooling means is not part of a recycling circuit, BHT will not condense upon and thus not clog the cooling means. Instead BHT is filtered out of the recycled air mixture within the foam block itself.
• TDI will also precipitate out of the cool mixed gasses in the second cooling step.
• the precipitated TDI is also filtered from the recycled air mixture and becomes trapped in the polyurethane block. This is ideal in that the TDI is returned to the block to undergo further cross-linking reactions.
• the recycling of cooling air in the second step of the present invention conserves costly TDI.
• the second cooling step of the present invention accounts for the majority of block cooling as the chilled air mixture effectively reduces the block temperature to about 100°F.
• a third cooling step of the present invention ambient air is once again drawn through the block.
• the ambient air is able to draw any remaining fumes away from the block and vent them into the atmosphere.
• the air utilized in the third step of the present invention may be dehumidified in order to prevent the air from incorporating additional water into the foam block.
• Block temperature during the third step generally remains at about 100 ° F.
• the condensation of sublimates such as BHT and TDI takes place only within the second cooling step. Foam block internal temperatures during the first step is well above the sublimation point of BHT and TDI. Therefore, redeposition of sublimates within the block is not possible.
• the third step discussed below, involves block temperatures well below the sublimation temperatures of BHT and TDI and therefore sublimates of these compounds are not present.
• the internal block temperature of the foam block drops to a temperature of from about 90 to 110 ° F at termination of the second cooling step.
• air is never recirculated through a recouperant unit or refrigerant coil in which BHT, TDI or other gas components may cause a blockage.
• the first cooling step (fume extraction stage) of the present invention provides for a continuous venting of ambient air through the foam block. Since the method of the present invention may utilize a polyurethane formulation including a decreased percentage, or no auxiliary blowing agents, direct venting of the first stage of the enclosed tunnel does not place high concentrations of toxic agents such as chlorofluorocarbons or other volatile chlorine containing compounds into the environment. The vented gases therefore comply with all government requirements, such as the Clean Air Act, without requiring additional treatment.
• the present method may utilize a polyurethane formulation having an increased percentage of water.
• the increased water content provides adequate foaming during initial urethane formation without necessitating auxiliary foaming agents.
• Additives such as softening agents may be utilized along with the so-called soft polyols to further obviate the use of auxiliary blowing agents.
• the present invention is able to utilize a polyurethane formulation which includes less TDI while achieving substantially the same degree of cross- linking (and thus stiffness and hardness) in a polyurethane foam block as compared to prior methods. Therefore the present invention is economical in that less TDI (i.e., lower indexes) can be used.
• the present invention includes an apparatus which is especially adapted and configured for practicing the above-described method.
• This apparatus comprises an enclosed tunnel and a conveyor means, such as a slat conveyor for transporting foam blocks through the enclosed tunnel.
• the apparatus provides rapid cooling, degassing and dehumidifying of initially cured porous foam material while minimizing emission of pollutants.
• the apparatus includes a conveyor means or transporting porous foam material from a site of initial cure to and through an enclosed cooling tunnel.
• the tunnel utilizes ambient air and cooled ambient air to remove heat, moisture and volatile gasses from the foam material while simultaneously conserving and redepositing valuable sublimates back into the foam.
• the enclosed tunnel includes a plurality of suction fans located outside and adjacent to the tunnel.
• the vacuum fans are connected to the tunnel by duct work. As the suction fans are actuated, air is drawn from the enclosed tunnel through the ductwork thereby forming a vacuum within the tunnel. The vacuum within the tunnel draws ambient air into the tunnel through openings located at opposite ends thereof.
• a cooling fan and chiller unit are also located outside and adjacent to the tunnel. The cooling fan directs ambient air through a cooling duct into the tunnel. Within the cooling duct, a cooling coil chilled by the chiller unit reduces the temperature of air passing through the duct into the tunnel.
• a slat conveyor provides a conveyor means for moving polyurethane blocks through a first, second and third section of the enclosed tunnel wherein the blocks are sequentially defumed, cooled and further defumed again.
• Figures 1 and 2 illustrate one example of an apparatus especially adapted for practicing the method of the present invention.
• Blocks of polyurethane foam 1 are placed on a slat conveyor 3 which transports the blocks from a loading point to, and eventually through an entrance opening 5 located at one end of the enclosed tunnel 7.
• These blocks are generally loaded on the conveyor just after a peak in the time/temperature curve illustrating the exothermic formation reaction of the polyurethane. Delaying cooling until this point assures sufficient polymerization of the polyurethane occurs before a rapid cooling process will commence.
• Conveyor 3 transports the blocks into an entrance opening 5 located at one end of the enclosed tunnel 7 wherein the block enters a first cooling (fume extraction) section 9 wherein the first step of the present method takes place.
• slat conveyor 3 includes a plurality of elongated rectangular members or slats 4, which are separated by a distance sufficient to allow gas to flow therebetween.
• the ends of the slats 4 are sealed by the use of gaskets 6, since the foam blocks do not cover the entire top surface of the slats 4. This arrangement causes cooling gas to be drawn through the foam blocks.
• Typical conveyor dimensions for 2 meter amide blocks are about 2.3 m (90 inches) in width with each gasket extending inwardly about 250 cm (10") from each side of the conveyor.
• the gaskets have a width sufficient to provide gas sealing properties when the slats are spaced at a distance of about 3mm (1/8") .
• a first suction fan 15 is located outside and adjacent to the first section of the enclosed tunnel.
• the first suction fan removes air from a first suction box 21 (that occupies a lower portion of the first section below the slat conveyor) , by means of a first vacuum duct 13.
• the duct forms an air conduit from the fan which passes through an opening 11 in a side wall of the first section of the enclosed tunnel below the slat conveyor. Thus a vacuum is formed within the first vacuum box.
• Plastic side films are fed into the tunnel with the blocks to create a side seal so that the path of the recirculating air through the blocks does not short circuit through the sides.
• the vacuum created by the first vacuum fan 15 in the vacuum box draws ambient air from the upper portion of the enclosed tunnel and then through the porous block. The ambient air is thereafter drawn into the first vacuum box 21 from which it is removed, through the first suction fan via the first vacuum duct 13.
• the exothermic curing process results in block internal temperature ranges of about 250 to 500°F, and usually from 370 to 400 ° F. As discussed above, at these temperatures, various components of the foam are present in the gaseous state. In addition, at these elevated temperatures, excess water remaining after initial foaming and curing of the polyurethane is present as water vapor. Ambient air passing through the block during the first cooling stage vents the gaseous materials and water vapor from the block, while at the same time, reducing the temperature of the block.
• first vacuum box From the first vacuum box, ambient air now heated and transporting a mixture of gasses and water vapor is drawn through the first vacuum duct 13 by the first suction fan 15 and thereafter vented through a first emission duct 16.
• the first emission duct conducts the heated mixture to an emission point 18 located above the enclosed tunnel through which the heated mixture of air, vapors, moisture and sublimates exit the apparatus.
• the temperature of the emitted gas mixture ranges from about 160 to 180°F. Since the first section removes water from the polyurethane block, free-end isocyanate termination by excess water is reduced.
• a second suction fan 25 is located adjacent and outside the second section of the tunnel. Adjacent to the second suction fan, a cooling fan 30 is located.
• a chiller unit 27 adjacent the cooling fan contains a heat exchanger which is utilized to reduce the temperature of cooling coils located in cooling duct 33. Coolant pipes 29 enter cooling duct 33 so as to provide a means for the heat exchanger to remove heat from the cooling coils.
• the cooling fan 30 draws ambient air into cooling duct 33 through which the air is conducted into a side of the second section of the enclosed tunnel at a level above that of the slat conveyor.
• cooling coils located therein (not shown) cooled via coolant pipes 29 reduce the temperature of the ambient air.
• the cool ambient air entering the second section is drawn through polyurethane blocks located on a portion of the conveyor positioned therein by means of a vacuum created (below the level of the conveyor) , in a second vacuum box 21 located therein.
• the vacuum of the vacuum box is provided by the second suction fan which evacuates air from the second vacuum box into a second vacuum duct 37. From the second suction duct 37, the second suction fan forces the air into return duct 35 which empties into an upper portion of the second section above the porous blocks therein.
• FIG 6 shows an internal view of the second section of the apparatus of the present invention.
• the second vacuum box 21 located under the conveyor 3 is evacuated by means of the second suction fan 25 drawing air out from the box through second vacuum duct 37.
• Cooled ambient air supplied by cooling fan 30 supplies fresh reduced temperature air to the second section as shown in Figures 1 and 2.
• the cooled air Once the cooled air enters the second section, it is drawn through polyurethane foam blocks located therein and into the vacuum box positioned under the conveyor.
• a recirculation occurs.
• the air passing into the second vacuum box is drawn by the second suction fan 25 through the second vacuum duct 37.
• the air is then returned to the upper portion of the second section of the enclosed tunnel through return duct 35.
• the second section of the apparatus provides for the recycling of cooled air through the polyurethane foam blocks in accordance with the second step of the method of the present invention.
• Polyurethane blocks conveyed through the second section exhibit temperatures beyond the sublimation temperature of various components of the polyurethane such as BHT and TDI. Since coolant air is recycled by the second suction fan and ducts 35 and 37, no venting and thus no loss of such sublimates occur in the second section.
• the cooled air introduced into the second section by the cooling fan 30 and the cooling coils is comprised of fresh ambient air. Since there is no recycling of air through duct 33, clogging of the cooling coils by BHT, TDI or other sublimates is avoided.
• the third suction fan 45 draws air from a third vacuum box 43 located in a lower portion of the third section of the enclosed tunnel below the level of the slat conveyor by means of an air conduit formed by the third vacuum duct 47. Thus, a vacuum is formed within the third vacuum box.
• the suction created in the third suction box draws ambient air through the exit opening located at an end of the enclosed tunnel opposite the entrance opening end.
• the ambient air is then drawn through foam block positioned on a portion of the conveyor located in the third section removing additional heat and sublimates therefrom.
• Air drawn through blocks positioned in the third section are conveyed through a third vacuum duct 47 to a second emission duct 49. As in the first section, heated air containing sublimates is vented to emission point 18 rather than being recycled.
• Figures 3a and 3b schematically compare different emissions resulting from utilizing polyurethane formulations with little or no auxiliary foaming agents and conventional formulations containing a substantial amount of these agents.
• Figure 3b schematically represents the process of the present invention applied to a polyurethane formulation having little or no auxiliary blowing agents.
• Figure Block 57 represents a polyurethane formulation especially adapted for use with the method of the present invention in which little or no auxiliary blowing agents are used.
• foam block formation such as in a vertical foam square machine as represented by block 61
• suction fans 63 vent gases 67 resulting from the polyurethane forming reaction. Since the formulation 57 contains little or no auxiliary blowing agents such as chloro luorocarbons, emission 67 will not include a substantial amount of these pollutants.
• Block 69 represents the rapid cooling process of the present invention wherein gas extraction provided by suction fans 64 vent gases containing little or none of the above discussed pollutants.
• Block 71 represents foam cure areas after rapid cooling.
• Final polyurethane foam blocks represented by box 85 exhibit hardness and stiffness equivalent to that provided by conventional polyurethane formulations utilizing a significant amount of auxiliary foaming agents. Thus these reduced blowing agent formulations result in decreased pollution during foam manufacture while yielding polyurethane products exhibiting excellent physical properties.
• Figure 3a schematically represents conventional processing of polyurethane formulations having a substantial amount of auxiliary blowing agent.
• Block 55 represents a conventional polyurethane foam formulation including a significant amount of auxiliary foaming agent.
• gas by-products are extracted by suction fans 66 resulting in emissions 65.
• the polyurethane formulation represented in Figure 3a includes a significant amount of auxiliary blowing agent, a substantial amount of pollutant, such as chlorofluorocarbons, will be generated at this stage of polyurethane foam block manufacture.
• Block 72 represents a conventional slow curing process.
• Suction fans 68 remove volatile gasses generated during the slow curing which, as during the initial foam curing process, will contain a significant amount of pollutants derived from the auxiliary blowing agents.
• Figure 7 schematically illustrates the air current paths utilized in the cooling process of the present invention as well as a graph depicting the decrease in polyurethane block temperature during the process.
• Block 9 represents the first section of the apparatus of the present invention in which ambient air 93 is drawn through the polyurethane block by first suction fan 15 and then vented at emission point 83.
• ambient air 93 is drawn through the polyurethane block by first suction fan 15 and then vented at emission point 83.
• the average temperature of vented gasses at this point range from 155 to 185 ° F.
• Circuit 95 illustrates the air circulation path occurring in the second section 17 of the apparatus of the present invention.
• Fresh ambient air 93 drawn into the enclosed tunnel by cooling fan 30 is constantly mixed with air which has been drawn through porous blocks located in the second section by the second suction fan 25.
• a cooled mixture is returned to the top of the second section for continuous recycling through the block.
• the temperature of the cooled air mixture returning to the top of the second section ranges from between 100 and 160 ° F.
• Circuit 97 represents air flow in the third section. Air from an upper portion of the tunnel is pulled through a foam block by the third suction fan 45 and out emission duct 85. The temperature of the gas removed from the third section is typically about 100 ° F.
• Graph 87 incorporated within the schematic diagram illustrated in Figure 7 represents the declining internal block temperature of a polyurethane block cooled in accordance with the method of the present invention.
• the initial peak temperature at point 85 ranges from about 370 to 400°F and decreases to about 100 ° F at point 90 by the beginning of the third step of the process.
• the time period required for rapid cooling of a polyurethane foam block . utilizing the apparatus and method of the present invention ranges from about 8 to 18 minutes.
• a vertical polyurethane foam block forming apparatus 100 is shown located adjacent the apparatus of the present invention.
• a roller conveyor 101 receives blocks from the vertical apparatus after a short holding time and transports them to the slat conveyor 3 for introduction into the enclosed tunnel 7 for rapid curing.
• an initial holding time of between about 5 minutes and one hour is beneficial, with 10 to 30 minutes being optimum. This initial holding time subjects the blocks to cooling only after developing sufficient properties to withstand the cooling process without shape distortion or deterioration.
• round block foam by the present invention.
• These round blocks are cut to an appropriate length and are placed with the cut side facing the slat conveyor.
• the entrance to the tunnel must be sufficient in width to accommodate the diameter of the block, and in height to accommodate the length of the block.
• a form or template is advantageouslyjplaced upon the slat conveyor 3 so that all cooling air is forced to pass through the foam block. Otherwise, the round blocks pass through the tunnel and are treated in the same manner as the rectangular blocks.
• the method of the present invention allows the use of a polyurethane formulation especially adapted for practicing the method.
• the polyurethane formulation of the present invention comprises a polyether polyurethane, an organic diisocyanate, water at least one softening agent.
• a higher percentage of water and a decreased amount of auxiliary blowing agent (as compared to prior art polyurethane foam formulations) , is advantageously utilized.
• These formulations may incorporate either diminished amounts of or no auxiliary foaming agents while producing urethane foam blocks exhibiting excellent smoothness, softness, and strength while decreasing the emission of toxic pollutant chlorofluorocarbons.
• polyether polyol as used through-out this application includes poly (oxytetramethylene) glycols which are prepared by the polymerization of tetrahydrofuran.
• Poly(oxypropylene) triols are another important group of polyethers used in this class. These triols are prepared by the same general reactions as poly (oxypropylene) glycols.
• the most preferred polyols for practicing the present invention include Thanol F-3020 as the 3000 m.w. polyether polyol, and Thanol F-1500 as the 1500 m.w. polyether polyol, both of which are manufactured by Arco Chemical. These were utilized in the examples as the basic polyol and soft polyol, respectively.
• organic isocyanate compound is used to describe the isocyanate or polyisocyanate compounds that are suitable for use in this invention.
• organic isocyanate compounds include aromatic, aliphatic, and cycloaliphatic polyisocyanates and combinations thereof.
• diisocyanates such as m-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, mixtures of 2,4 toluene and 2,6-toluene diisocyanate, tetramethylene diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate (and isomers) , naphthalene-1,5-diisocyanate, l-methoxyphenyl-2,4- diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'- biphenylene diisocyanate, 3,3-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethoxy-4,
• amide terminated isocyanates may be controlled.
• the mixture is comprised of a basic polyol having a molecular weight of at least about 2,500 to 4,000, preferably about 3,000, with a soft polyol with a molecular weight of from about 1200 to 1800, and preferably about 1500.
• the hydroxyl functionality of the basic polyol is between about 30 to 80, preferably about 56, while the functionality of the soft polyol is between about 90 and 150, preferably about 112.
• Amide formation decreases smoothness and softness of a polyurethane foam product.
• Soft polyol utilize in a polyurethane formulation especially adapted for the present method, greatly reduces amide formation.
• even a reduced amount of amide terminated diisocyanate compounds may unfavorably effect polyurethane texture if allowed to agglomerate.
• a sodium salt of polyacrylic acid is advantageously utilized in the above-discussed formulation as a dispersant electrolyte effectively preventing such agglomeration.
• both soft polyol and the dispersant in the polyurethane formulation, only a small quantity of well dispersed amide terminated diisocyanates will form in the final polyurethane foam product produced in accordance with the present method. This amount ranges from about 0.1 to 1 weight percent of the formulation, preferably about 0.3 to 0.7 weight percent.
• additives for forming the foam which may be incorporated into these form foaming compositions are well known to those skilled in the art, and would include, for example, catalysts, chain extending agents, surfactants or surface active agents, and/or flame retardant additives.
• Suitable flame retardan s for use in the composition of the invention include those which are conventionally used in the art of making flexible, flame retardant polyurethane foams, such as triesters of phosphoric acid, halogenated triesters of phosphoric acid, halogenated hydrocarbons, and the like.
• Example 1
• Table 1 lists the components of a polyurethane formulation of the prior art (Old-1) and two polyurethane compositions (New-1 and New-2) especially formulated for use in the method of the present invention.
• the parts by weight of water in the new formulations are greater than that utilized in the old formulation (4.255).
• the incorporation of a greater amount of water in the polyurethane formulation utilized with the method of the present invention allows for greater foaming, but has previously been limited due to isocyanate termination caused by excess water.
• the first new formulation (New 1) includes 80 parts basic polyol and 20 parts soft polyol.
• the basic polyol refers to a polyol with a molecular weight of about 3,000 whereas the soft polyol has a molecular weight of about 1500.
• the increased availability of hydroxyl groups on the soft polyol provide additional cross-linking sites for the isocyanate groups of diisocyanates used in the formulation.
• New formula 1 and 2 utilize a greater percentage of water, hardening of the foam material through formation of an excess number of amide groups (resulting from termination of isocyate groups by water) does not occur.
• the soft polyol acts to non-competitively bind isocyanate groups that would otherwise react with the water thereby providing a softer foam product.
• Carapor 2001 is a softening agent comprising a sodium salt of polyacrylic acid. Since the new formulations utilize a greater amount of water, some increase in the amount of amide diisocyanate formed as a result will occur. In order to prevent these amide terminated diisocyanate groups from increasing the hardness of the foam product, Carapor is added to the formulations as a dispersant which prevents agglomeration of these groups.
• the TDI index a ratio of isocyanate groups theoretically available in the starting formula for reaction with polyol hydroxyl groups demonstrates the efficiency of the method of the present invention.
• Table 1 lists a TDI index for Old-1 as being 108, or 108 isocyanate groups for every 100 hydroxyl groups with which they can react. This TDI index indicates that an excess of available isocyanate groups was required in past polyurethane foam formulations because of the loss of a substantial amount of TDI as a sublimate during exothermic curing.
• the two new polyurethane compositions listed in Table 1 exhibit a lower TDI index.
• these new formulation provide an adequate amount of isocyanate groups to complete cross-linking of the polyurethane when cured according to the method of the present invention.
• these new formulations utilize a decreased amount of expensive TDI, while the resultant foam products demonstrate stiffness and harnesses which are equivalent to those provided by foam products made from the old formulation.
• Table II lists various physical property results for the low density/low indentation polyurethane foam formulations of Table I.
• the physical property results were obtained from the three polyurethanes represented in Table I after first being subjected to initial curing and then the rapid curing method of the present invention. Actual testing took place approximately 24 hours after completion of rapid cure.
• tear strength, tensile strength and indentation load deflection (all indicative of the degree of cross-linking achieved in the polyurethane) , of the old formulation and New-1 are substantially equivalent. This is surprising in that the TDI index for New-1 was about 6% lower than that of the old formulation.
• the New-2 formulation demonstrated a significant decrease in tensile strength, its indentation load deflection as well as its tear strength were substantially the same as the other two formulations.
• the percentage of elongation of the New-2 formulation was the lowest indicating a greater degree of cross-linking then would be expected in the formulation with the lowest TDI index.
• Figure 8 is a time/temperature graph illustrating the rapid curing of the old formulation listed in Table I according to the method of the present invention.
• the conveyor speed in the enclosed tunnel was approximately 3.63 feet/minute.
• Ambient temperature during rapid cooling was 87°F at a relative humidity of 38%.
• the tunnel temperature was 115°F. Twelve minutes were required to cool the foam.
• Figure 9 is a time/temperature graph illustrating the rapid curing of the formulation listed as New-1 in Table I especially formulated for the method of the present invention.
• Conveyor speed was 3.62 feet/minute.
• the ambient temperature was 71 ° F at a relative humidity of 49%.
• the tunnel temperature was 118°F at a relative humidity of 28%.
• the cold air temperature was 36°F. Fifteen minutes were required to cool the foam.
• Figure 10 is a time/temperature graph illustrating the rapid curing of the formulation listed as New-2 in Table I especially formulated for the method of the present invention.
• Slat conveyor speed was 3.88 feet/minute.
• the ambient temperature was 75 ° F at a relative humidity of 49%.
• the tunnel temperature was 118°F at a relative humidity of 28%.
• the cool ambient air temperature was 36°F.
• Table III lists the components of a low density/high indentation load deflection polyurethane formulation of the prior art (Old-2) and two polyurethane compositions (New-3 and New-4) especially formulated for use in the method of the present invention.
• the parts by weight of water in the new formulations are greater than that utilized in the old formulation (6.012).
• Methylene chloride an auxiliary foaming agent is present (parts per weight) , in either a reduced amount or absent in the two new formulations (5.020 and 0) as compared to the old formulation (8.768) .
• This reduced amount of agent in the new formulations does not deleteriously affect the degree of polyurethane foaming (as discussed below) , since a greater percentage of water in the new formulations provides adequate foaming.
• Table III lists a TDI-index for the Old-2 formulation as being 118, or 118 isocyanate groups for every 100 hydroxyl groups with which they can react.
• the two formulations New-3 and New-4 especially adapted for use in the method of the present invention exhibit a decreased TDI index of 110 and 104 respectively. Yet, as discussed below, these new formulations still exhibit satisfactory cross linking.
• Table IV lists various physical property results for the low density/high indentation load deflection polyurethane foam formulations described in Table III. The physical property results were obtained from the three polyurethanes represented in Table I after first being subjected to initial curing and then the rapid curing method of the present invention. Actual testing took place approximately 24 hours after completion of rapid cure.
• FIG. 11 is a time/temperature graph illustrating the rapid curing of the formulation listed as Old-2 in Table III. Slat conveyor speed was 4.16 feet/minute. The ambient temperature was 93 ° F at a relative humidity of 32%. The tunnel temperature was 13° ° F. Fifteen minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Figure 12 is a time/temperature graph illustrating the rapid curing of the composition listed as New-3 in Table III especially formulated for the method of the present invention.
• Slat conveyor speed was 4.04 feet/minute.
• the ambient temperature was 55°F at a relative humidity of 56%.
• the tunnel temperature was 124°F.
• the cooling duct supplied 36°F air at 560 cfm to the enclosed tunnel. Nine minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Figure 13 is a time/temperature graph illustrating the rapid curing of the composition listed as New-4 in Table III especially formulated for the method of the present invention.
• Slat conveyor speed was 4.36 feet/minute.
• the ambient temperature was 68°F at a relative humidity of 40%.
• the cooling duct supplied 35-38°F air at 1000 cfm to the enclosed tunnel. Twelve minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Table V lists the components of a medium density/high indentation load deflection polyurethane formulation of the prior art (Old-3) and a polyurethane composition (New-5) especially formulated for use in the method of the present invention.
• the parts per weight of water in the new formulation (4.567) is greater than that utilized in the old formulation (4.179).
• Methylene chloride an auxiliary foaming agent is not present in the new formulation and is present in the old formulation (2.924).
• the absence of this auxiliary blowing agent in New-5 does not deleteriously affect the degree of polyurethane foaming since a greater percentage of water in the new formulation provides adequate foaming.
• Table V lists a TDI index for the Old-3 formulation as being 116, or 116 isocyanate groups for every 100 hydroxyl groups with which they can react.
• the new formulation New-5 especially adapted for use in the method of the present invention exhibits a decreased TDI index of 102. Yet, as discussed below, this new formulation still exhibits satisfactory cross linking.
• Table VI lists various physical property results for the medium density/high indentation l.oad deflection polyurethane foam formulations of Table V.
• the physical property results were obtained from the two polyurethanes formulations represented in Table V after being subjected to initial curing and the rapid curing method of the present invention. Actual testing took place approximately 24 hours after completion of rapid cure.
• Figure 14 is a time/temperature graph illustrating the rapid curing of the composition listed as Old-3 in Table V.
• Slat conveyor speed was 3.46 feet/minute.
• the ambient temperature was 72°F at a relative humidity of 75%.
• the cooling duct supplied 43°F cool air at 1062.5 cfm to the enclosed tunnel. Fifteen minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Figure 15 is a time/temperature graph illustrating the rapid curing of the composition listed as New-5 in Table V.
• Slat conveyor speed was 3.41 feet/minute.
• the ambient temperature was 53°F at a relative humidity of 64%.
• the cooling duct supplied 38°F air at 500 cfm to the enclosed tunnel. Approximately 15 minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Table VII lists the components of a high density/high indentation load deflection polyurethane formulation of the prior art (Old-4) and two polyurethane compositions (New-7 and New-8) especially formulated for use in the method of the present invention. - Table VII
• the parts by weight of water in the new formulations is greater than that utilized in the Old formulation (2.697).
• Methylene chloride, an auxiliary foaming agent is not present in New-8 and is present in an amount (2) which is significantly less than that included in the Old-4 formulation (5) .
• the absence or reduction of this auxiliary blowing agent in the new formulations does not deleteriously affect the degree of polyurethane foaming since a greater percentage of water provides adequate foaming.
• Table VII lists a TDI index for the Old-4 formulation as being 112, or 112 isocyanate groups for every 100 hydroxyl groups with which they can react.
• the new formulations New-7 and New-8 especially adapted for use in the method of the present invention exhibit a decreased TDI index of 103 and 100 respectively. Yet, as discussed below, when cured according to the method of the present invention, these new formulation still exhibit satisfactory cross linking.
• Table VIII lists various physical property results for the high density/high indentation load deflection polyurethane foam formulations of Table VII. The physical property results were obtained from the two polyurethanes represented in Table I after being subjected to initial curing and the rapid curing method of the present invention. Actual testing took place approximately 24 hours after completion of rapid cure.
• Figure 16 is a time/temperature graph illustrating the rapid curing of the composition listed as Old-4 in Table VII.
• Slat conveyor speed was 2.34 feet/minute.
• the ambient temperature was 75°F at a relative humidity of 78%.
• Nine minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Figure 17 is a time/temperature graph illustrating the rapid curing of the composition listed as New-6 in Table VII.
• Slat conveyor speed was 2.61 feet/minute.
• the ambient temperature was 49°F at a relative humidity of 49%.
• the cooling duct supplied 37°F air at 500 cfm to the enclosed tunnel. Approximately 8 minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.
• Figure 18 is a time/temperature graph illustrating the rapid curing of the composition listed as New-7 in Table VII.
• Slat conveyor speed was 2.52 feet/minute.
• the ambient temperature was 49°F at a relative humidity of 41%.
• the cooling duct supplied 36°F air at 500 cfm to the enclosed tunnel. Approximately 9 minutes were required for the rapid cure to complete the cooling of the polyurethane blocks.

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